In reduced pressure chemical vapor deposition reaction chambers, particulate contaminants within the reaction chamber can cause flaws in any deposition process. One source of particles arises from mechanical systems within the reaction chamber, such as actuators for supporting the workpiece on which the process is to take place. In complex systems, which require both elevation, or linear motion, of the workpiece, and rotation of the workpiece, these actuators typically require a rotary feed-through device for rotating a support member, and a vacuum bellows which allows linear motion of the workpiece and support member itself relative to the reaction chamber. Vacuum bellows are a notorious source of particulate contaminants in such systems. In addition, they cannot be purged effectively or cooled.
One system which utilizes the vacuum bellows in combination with rotary feed-through is illustrated in co-pending U.S. patent application Ser. No. 07/351,829, referred to above.
FIG. 1 of the present application is a schematic diagram of a prior art rotary/linear actuator, such as used in the system disclosed in the cross-referenced application Ser. No. 07/351,829. FIG. 1 illustrates the chemical vapor deposition reaction apparatus of the cross-referenced application which includes a lamp housing 10 which generates reaction energy for supply into a reaction region 11 of the reaction chamber 12. Reaction gases are supplied into plenum 13 and from plenum 13 into the reaction region 11. A workpiece 14 is mounted on a support member 15, which orients the workpiece in the reaction region 11 to receive the reaction energy and the flow of reaction gases. The support member is mounted to a rotatable shaft 16 which is coupled to a rotary feed-through mechanism 17, such as a rotary feed-through, such as commercially available from Ferro-fluidic Inc. A motor 18 is used to control the speed of rotation of the workpiece 14. In this embodiment, the shaft 16 is hollow.
In order to position the workpiece 14 linearly within the reaction region 11, a vacuum bellows 19 is formed on the wall of the reaction chamber. The reaction region 11 is moved up and down with respect to the workpiece 14 by means of ball screws 20. Only one ball screw 20 is shown in this diagram for simplicity.
In this system using a prior art actuator design, particles escape from the rotation and translation mechanism, and particularly from the bellows 19, into the reaction region 11 of the reaction chamber 12.
This reaction chamber 12 is a reduced pressure reaction system, having an exhaust outlet 21 which is coupled to vacuum pump to remove exhaust gases and gas borne particles from the system. The exhaust system however does not completely prevent contamination of the workpiece 14.
Accordingly, it is desirable to provide a rotary/linear actuator which eliminates the necessity of vacuum bellows, and otherwise reduces particulate contaminates in the reaction apparatus. Also, it is desirable to provide a rotary/linear actuator which can be cooled and purged.